The present invention relates to a method for continuously producing a non-woven web from filaments of natural or synthetic fiber. More particularly, it relates to a method for continuously producing a non-woven web having uniform distribution of the filaments by drafting the filaments with a high speed air-jet type drafting device.
It is well known in the art to produce a non-woven web by means of an air-jet type drafting device (generally referred to as "air sucker"), drafting in high speed air flows a multiple number of filaments which are led from a filament source in the form of spinning nozzles or raw filaments on bobbins, and blasting the drafted yarns against a horizontally moving collector (normally, a wire mesh conveyor) which is located beneath the drafting device. The web producing method using as a filament source spinning nozzles each with a multiple number of orifices for melt-spinning and drafting the resultant synthetic fiber by an air sucker is known as a "spun bond method," which is generally favorably accepted because of uniform distribution of filaments in the web, high productivity and low production cost. However, with the recent extension of utilities of the non-woven webs as a base cloth in various industrial fields, there has been requested non-woven webs having a higher uniformity.
As an example of a device used for the spun bond method, i.e. for drafting filaments in the form of a curtain which are obtained by melt-spinning a synthetic resin through spinning nozzles having a multiple number of orifices, there has already been proposed a combination of an air jetting device, by which high speed air jets (compressed air) are once blasted from opposite sides onto the filaments in such a jetting angle that the component force of the air jets in the moving direction of the filaments becomes far larger than that in the right angle direction, and a filament-drafting device which is located beneath the air jetting device and is provided with narrow guide passages for guiding the filaments and air stream (Japanese Patent Publication No. 38,025/1973). In this method using the air jetting device and the filament-drafting device, the high speed air jets are applied to the filaments in the form of a curtain from opposite sides only one time in order to avoid the entanglement of the filaments. Any slight variation in the gap space of the air jet spouting slits of this device results in non-uniform blasting action of the air jets on the filaments and thus in non-uniform webs. Of course, it is technically possible to maintain a uniform gap at the respective jet spouting slits by resorting to an additional slit adjusting mechanism. However, high precision work is required in machining its respective component parts. This problem naturally will lead to high installation costs and maintenance expenses and are eventually reflected by higher production costs of the webs. Moreover, the guide passage for passing through of the filaments should also be provided in a highly precise dimension. Even if these parts of the device are provided in a highly precise dimension, the uniform distribution of the filaments is lost, for instance, by a slight variation of the conditions for cooling the filaments or by a small deposit onto the filament guide passage of the drafting device, and it is necessary to remove various causes of inducing such a non-uniformity of the filaments deposited on the collector, but it is very difficult.
The present inventors have intensively studied to find an improved method for producing a non-woven web having uniform distribution of the filaments by using the above device, and it has now been found that the desired web can be produced by drafting the filaments in the form of a curtain from a filament source with a high speed air-jet type drafting device via a filament distribution-controlling device equipped with a filament guide passage having a narrow rectangular cross section and plural sucking means which are provided at least at one rectangular side wall of the filament guide passage.
An object of the present invention is to provide an improved method for producing non-woven webs having uniform distribution of filaments.
Another object of the invention is to provide an improvement in the drafting of the filaments with a high speed air-jet type drafting device in order to avoid the non-uniformity of the filaments stream or the entanglement of the filaments.
A further object of the invention is to provide a filament distribution-controlling device for controlling the stream of the filaments drafted with a high speed air-jet type drafting deice.
These and other objects of the invention will be apparent from the following description.
The method for continuously producing non-woven webs having uniform distribution of filaments of the present invention comprises drafting filaments in the form of a curtain from a filament source with a high speed air-jet type drafting device via a filament distribution-controlling device and blasting the filaments thus drafted onto a collector.